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5.12 For heating appliances and combined appliances, when it is specified that the: B) _0 x( z, p/ [+ G4 N2 {
appliance has to operate at a power input multiplied by a factor, this applies only to heating V4 r3 {6 g9 i( O) {# a J5 Z
elements without appreciable positive temperature coefficient of resistance. A- [$ \1 m1 w( R3 b! w
For heating elements with appreciable positive temperature coefficient of resistance, other than: L- K5 ^0 q. C# N. B
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
( I$ J3 }3 B3 @ C5 D$ dvoltage until the heating element reaches its operating temperature. The supply voltage is then; \( Y M6 W$ Y1 F
Copyright International Electrotechnical Commission
( a% e+ y& a0 i1 P1 m( wrapidly increased to the value necessary to give the power input required for the relevant test,
/ U! W9 r2 ?4 {" C& H+ F( sthis value of the supply voltage being maintained throughout the test.
% A% N0 [* a; c) C ^ h0 V% lNOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input1 X) g J; k- f; I/ O7 @; I5 |
of the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
$ v, Q p8 W* O0 Q/ D. m5.13 The tests for appliances with PTC heating elements and for heating appliances and
# R/ J3 w, U8 a# |. \* v! I* J& Y( V& Q' lcombined appliances where the heating elements are supplied via a switch mode power
, o$ ~$ p& b9 r4 M# M1 Qsupply are carried out at a voltage corresponding to the specified power input.
, F! b# u/ @1 bWhen a power input greater than the rated power input is specified, the factor for multiplying8 ^3 W( ^6 `. C
the voltage is equal to the square root of the factor for multiplying the power input. |
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发表于 2012-10-14 22:14
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